This invention generally relates to plunger tips for syringes and, more particularly, to a dual material plunger tip having a solid core for use with a syringe.
Typically, syringes have plunger tips that are made entirely from a single elastomeric material. Such elastomeric plunger tips may tend to interact with the contents of the syringe, leading to breakdown of the plunger tip and contamination of the syringe contents. Additionally, there is a tendency for elastomeric plunger tips, when left in one position for an extended period of time, to “set” in that position. That is, the elastomeric plunger tip sticks to an inner wall of the syringe barrel, such that an increased force is required to break the adhesion between the plunger tip and the inner wall and begin movement of the plunger tip within the syringe barrel. Also, because of the flexible nature of elastomeric plunger tips, the mechanical connection between the plunger and the plunger tip may tend to be relatively unstable, such that the plunger can move with respect to the plunger tip. Such movement can potentially cause the misalignment of the plunger and the plunger tip, which could result in uneven pressure on the plunger tip during use of the syringe.
Therefore, it is desirable to have a plunger tip that is not completely made of an elastomeric material, replacing at least some of the elastomeric material with another material, such as an inert polymeric material. In this way, the amount of surface area of the elastomeric material in contact with the contents of the syringe is reduced, leading to less potential breakdown of the plunger tip and less potential contamination of the syringe contents. Also, it is desirable to have such a plunger tip that reduces the amount of elastomeric material in contact with the inner wall of the syringe barrel to reduce the amount of “setting” of the elastomeric material and, in turn, reduce the amount of force required to begin movement of the plunger tip within the syringe barrel. Lastly, it is desirable to use a more rigid material within the plunger tip in order to provide a more rigid connection between the plunger and the plunger tip, thereby reducing the likelihood of misalignment of the plunger tip and plunger, leading to the exertion of uneven pressure on a loose plunger tip.